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Commit 9a265114 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

mm: vmscan: clean up get_scan_count() 



Reclaim pressure balance between anon and file pages is calculated
through a tuple of numerators and a shared denominator.

Exceptional cases that want to force-scan anon or file pages configure
the numerators and denominator such that one list is preferred, which is
not necessarily the most obvious way:

    fraction[0] = 1;
    fraction[1] = 0;
    denominator = 1;
    goto out;

Make this easier by making the force-scan cases explicit and use the
fractionals only in case they are calculated from reclaim history.

[akpm@linux-foundation.org: avoid using unintialized_var()]
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Satoru Moriya <satoru.moriya@hds.com>
Cc: Simon Jeons <simon.jeons@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 11d16c25

mm/vmscan.c

+44 −21
Original line number Original line Diff line number Diff line
@@ -1638,6 +1638,13 @@ static int vmscan_swappiness(struct scan_control *sc) 
	return mem_cgroup_swappiness(sc->target_mem_cgroup);

	return mem_cgroup_swappiness(sc->target_mem_cgroup);

}

}





enum scan_balance {

	SCAN_EQUAL,

	SCAN_FRACT,

	SCAN_ANON,

	SCAN_FILE,

};



/*

/*

 * Determine how aggressively the anon and file LRU lists should be

 * Determine how aggressively the anon and file LRU lists should be

 * scanned.  The relative value of each set of LRU lists is determined

 * scanned.  The relative value of each set of LRU lists is determined
@@ -1650,14 +1657,16 @@ static int vmscan_swappiness(struct scan_control *sc) 
static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,

static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,

			   unsigned long *nr)

			   unsigned long *nr)

{

{

	unsigned long anon, file, free;

	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;

	u64 fraction[2];

	u64 denominator = 0;	/* gcc */

	struct zone *zone = lruvec_zone(lruvec);

	unsigned long anon_prio, file_prio;

	unsigned long anon_prio, file_prio;

	enum scan_balance scan_balance;

	unsigned long anon, file, free;

	bool force_scan = false;

	unsigned long ap, fp;

	unsigned long ap, fp;

	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;

	u64 fraction[2], denominator;

	enum lru_list lru;

	enum lru_list lru;

	bool force_scan = false;

	struct zone *zone = lruvec_zone(lruvec);





	/*

	/*

	 * If the zone or memcg is small, nr[l] can be 0.  This

	 * If the zone or memcg is small, nr[l] can be 0.  This
@@ -1676,9 +1685,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 




	/* If we have no swap space, do not bother scanning anon pages. */

	/* If we have no swap space, do not bother scanning anon pages. */

	if (!sc->may_swap || (nr_swap_pages <= 0)) {

	if (!sc->may_swap || (nr_swap_pages <= 0)) {

		fraction[0] = 0;

		scan_balance = SCAN_FILE;

		fraction[1] = 1;

		denominator = 1;

		goto out;

		goto out;

	}

	}
@@ -1690,9 +1697,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 
	 * too expensive.

	 * too expensive.

	 */

	 */

	if (!global_reclaim(sc) && !vmscan_swappiness(sc)) {

	if (!global_reclaim(sc) && !vmscan_swappiness(sc)) {

		fraction[0] = 0;

		scan_balance = SCAN_FILE;

		fraction[1] = 1;

		denominator = 1;

		goto out;

		goto out;

	}

	}
@@ -1702,9 +1707,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 
	 * (unless the swappiness setting disagrees with swapping).

	 * (unless the swappiness setting disagrees with swapping).

	 */

	 */

	if (!sc->priority && vmscan_swappiness(sc)) {

	if (!sc->priority && vmscan_swappiness(sc)) {

		fraction[0] = 1;

		scan_balance = SCAN_EQUAL;

		fraction[1] = 1;

		denominator = 1;

		goto out;

		goto out;

	}

	}
@@ -1722,9 +1725,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 
	if (global_reclaim(sc)) {

	if (global_reclaim(sc)) {

		free = zone_page_state(zone, NR_FREE_PAGES);

		free = zone_page_state(zone, NR_FREE_PAGES);

		if (unlikely(file + free <= high_wmark_pages(zone))) {

		if (unlikely(file + free <= high_wmark_pages(zone))) {

			fraction[0] = 1;

			scan_balance = SCAN_ANON;

			fraction[1] = 0;

			denominator = 1;

			goto out;

			goto out;

		}

		}

	}

	}
@@ -1734,12 +1735,12 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 
	 * anything from the anonymous working set right now.

	 * anything from the anonymous working set right now.

	 */

	 */

	if (!inactive_file_is_low(lruvec)) {

	if (!inactive_file_is_low(lruvec)) {

		fraction[0] = 0;

		scan_balance = SCAN_FILE;

		fraction[1] = 1;

		denominator = 1;

		goto out;

		goto out;

	}

	}





	scan_balance = SCAN_FRACT;



	/*

	/*

	 * With swappiness at 100, anonymous and file have the same priority.

	 * With swappiness at 100, anonymous and file have the same priority.

	 * This scanning priority is essentially the inverse of IO cost.

	 * This scanning priority is essentially the inverse of IO cost.
@@ -1792,9 +1793,31 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 




		size = get_lru_size(lruvec, lru);

		size = get_lru_size(lruvec, lru);

		scan = size >> sc->priority;

		scan = size >> sc->priority;



		if (!scan && force_scan)

		if (!scan && force_scan)

			scan = min(size, SWAP_CLUSTER_MAX);

			scan = min(size, SWAP_CLUSTER_MAX);



		switch (scan_balance) {

		case SCAN_EQUAL:

			/* Scan lists relative to size */

			break;

		case SCAN_FRACT:

			/*

			 * Scan types proportional to swappiness and

			 * their relative recent reclaim efficiency.

			 */

			scan = div64_u64(scan * fraction[file], denominator);

			scan = div64_u64(scan * fraction[file], denominator);

			break;

		case SCAN_FILE:

		case SCAN_ANON:

			/* Scan one type exclusively */

			if ((scan_balance == SCAN_FILE) != file)

				scan = 0;

			break;

		default:

			/* Look ma, no brain */

			BUG();

		}

		nr[lru] = scan;

		nr[lru] = scan;

	}

	}

}

}